Fresh from giving his players a rollicking Jose Mourinho’s focus turns from Manchester United’s derby defeat to European action with a tricky Europa League opener at in-form Feyenoord on Thursday.

It will be the Portuguese manager’s first game in the second-tier European competition since winning its predecessor the UEFA Cup with Porto in 2003 and he says he is taking it seriously.

Mourinho’s unbeaten start as United manager came to a stuttering stop Saturday as long-time nemesis Pep Guardiola’s Manchester City left Old Trafford with a 2-1 victory.

United can expect a tough Group A opener at Feyenoord, who are top of the Dutch league having won all five of their matches this season and have pedigree in the competition.

United’s Spanish attacking midfielder Juan Mata warned that after the disappointment of derby day there was “no time for mourning”.

“On Thursday we’re going to play the first game in the Europa League, away against Feyenoord, a classic in European football,” Mata said on his weekly blog.

“It’s going to be a very demanding debut in this competition,” he added of the road to the final in Stockholm next May.

Mourinho says that young attacking sensation Marcus Rashford will play after his impressive second-half cameo along with midfielder Ander Herrera on Saturday.

“He (Rashford) is going to play is the only thing I can say. I trust him completely and I know his future will be absolutely brilliant,” said the Portuguese, who was scathing of some of his players after the City defeat, particularly defender Eric Bailly.

English-Dutch clashes are always feisty affairs but United have beaten Feyenoord in both their previous meetings.

This time it will be more subdued — at least in the stands — with the capacity of the De Kuip stadium in Rotterdam halved to 26,000 following UEFA sanctions for crowd trouble against Roma earlier this year.

United fans, whose ticket allocation has been slashed to 1,400, have been advised by the club not to wear United colours and avoid areas of potential conflict.

Feyenoord manager Giovanni Van Bronckhorst said: “I’m confident that -– in spite of the measures the club has to take –- an atmosphere will be created again at De Kuip to ensure we, as a team, are able to perform at our very best in our home matches.”

Former United and Feyenoord striker Robin van Persie is set to play both clubs as his Fenerbahce side are also in Group A with the Turkish side taking on Zorya Luhansk of Ukraine in their opener.

Van Persie won the competition with boyhood club Feyenoord in 2002.